According to Lhasa Railway Station that the booking on the Lhasa Shigatse Train are now bookable 30 days priror to departure. For the moment, there are 3 scheduled trains on this route, of which are: Z8801/2, Z8803/4, and Z9802

Following the national train department regulation of “Real-Name System” that the orignal copy of your ID or passprot is reuqired when purchasing the tickets;
The tickets can now be booked 30 days days priror to departure; and can be booked online or by a phone booking